1. Field of the Invention
The present invention relates to an improvement to binding files of the type which comprise a front sheet, a rear sheet and a back portion, wherein at least the back portion is made of a relatively porous material, for instance cardboard, and an amount of glue which melts under the influence of head is provided on an inner side of the back portion.
2. Description of the Related Art
In the present case, binding file is understood to mean both proper files and parts thereof, for instance parts which mainly consist of a back portion of the file with small projections to which a front sheet and/or a rear sheet may be attached.
In order to bind a bundle of sheets, documents or the like by such known binding files, these sheets or the like are placed between the front and the rear sheet of the file so that they are brought with one edge into contact with the above-mentioned amount of glue.
Subsequently, the whole is put vertically on a heating element with the back portion downward in such a manner that the glue melts and the sheets to be bound penetrate into the glue so that, after the binding file has been removed from the heating element and the glue has solidified, the sheets are firmly held in the binding file.
A serious disadvantage of binding files having the back portion made of a porous material, for instance cardboard, is the fact that when the glue melts, it is partly absorbed by the porous material. The glue penetrates into the pores of this material causing the amount of glue which remains available for the actual fastening of the sheets to be reduced.